The art and science of interventional therapy and surgery has continually progressed towards treatment of internal defects and diseases by use of ever smaller incisions or access through the vasculature or bodily openings to reduce tissue trauma surrounding the treatment site. One important aspect of such treatments involves percutaneous placement of stents or scaffolds at a given treatment site (or sites).
Stents are typically introduced within a vessel in a collapsed configuration and then expanded when placed in the vessel to maintain patency of the vessel. Stent expansion is either memory-based (i.e., self-expanding), deformation-based (i.e., balloon expanding), or a combination of both. Stents that are expanded using deformation-based techniques include areas of concentrated stresses in predetermined areas to control the deformation. For example, balloon-expandable stents have high stress areas in the hinges to facilitate controlled crimping and subsequent expansion.
As a result of this construction, however, when applied, the stresses are the highest in these areas, such as in the expanded state under radial load from the vessel or bodily openings. In the case of polymeric stents or scaffolds, these concentrated stress areas can be subject to deformation due to the viscoelastic properties of the polymer material, thus leading to undesirable and deleterious effects to the stent (i.e., stent collapse or recoil).